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Saito FG-84R3 Operating Instructions Manual Page 5

4-stroke gasoline radial engine.
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(3) Refill the tank and run the engine with the main needle to achieve peak and less speed (richer) alternately about 5 times.
And then maintain the peak condition long gradually. When it gets stable, then operate the throttle stick to vary slow speed
to high speed several times to check the response. After that run it for 1 tank keeping high speed.
(4) When it comes to run smoothly at peak, break-in on the ground is completed. Then perform tappet adjusting referring to
Chapter 13 and adjust the carburetor referring to Chapter 12. After that, fly it for about 20 times in rich condition to finish
break-in in the air.
Also after break-in, please run the engine in rich condition as long as it doesn t affect to the flight.
Note : During early stage of flights, take the height high enough to land safely in case the engine stop in the air suddenly. It
will reduce the risk of crash or landing accident.
12. Adjustment of carburetor
Before adjustment, please set both needles as the standard values.
In principle, the carburetor should first achieve peak by adjusting the main needle. Then performing idling with the throttle
valve and the slow needle. (Unless the peak is certainly achieved, idle adjustment will be difficult and not stabilized.)
*The slow needle is set as to keep around 1,300 1,500rpm at idling at factory default.
(1) After filling up the fuel tank, start the engine as described in Chapter 10 and run it for 1 minutes in rich condition. Then fully
open the throttle valve with the throttle stick.
(2) By turning the main needle with the adjustment bar observing tachometer and exhaust sound, achieve peak carefully.
Caution : Too much throttling the main needle is very dangerous because it might cause knocking and the prop nut might be came
off. Once you notice abnormal vibration or sound during throttling the main needle, just return to open the needle immediately.
(3) Next, close the throttle valve until the engine runs stably with an idling rotation around 1,300rpm by adjusting the slow
needle with the adjustment bar carefully. (During flight, it s rather stable with slightly high adjusted at idling. )
*The best richness of the air-fuel mixture at slow speed is depend on the flight style. Generally, Scale flight requires stability in
low speed so slightly lean condition is preferable. On the other hand Acrobatic flight requires quick response from low
through high, so slightly rich condition is preferable.
(4)Once the idling is set, get the throttle valve fully opened gradually. If the revolution becomes slow or goes up suddenly,
adjust the slow needle carefully until rpm raises linearly from idling to peak by fine-tuning.
(5)After adjustment of (4) is completed, perform the process from idling to peak quickly. If revolution gets delayed to achieve
peak even if the throttle valve is fully opened, fine-tune the main needle and perform the same process. Repeat this
fine-tune and response check carefully until the response improves.
*Tip for adjustment of the slow needle is to make lean as possible as the engine don t get stole when open the throttle valve
quickly. At the same time, since a gas-engine has narrow range of air-fuel ratio, adjustment of the needles is stricter than a
glow-engine. And both needles are interfered slightly from each other so confirm the balance of peak and response after
*To keep the engine life longer, adjust the fuel mixture as rich as possible in the range it doesn t affect to the running. Carb
adjustment is affected by many factors such as prop, flight style, atmosphere (humidity, temperature, ...) ,oil, plug, fuel, and
so on. Please keep trying to find the best condition to match your plane.
Throttle lever
Slow needle
to rich
to lean
13. Normal operation, maintenance, and additional information
(1) Just after start up the engine, perform warm up running in rich condition for about 1 minute, and just before stop run it at
idling for 1 minute to cool down as well. When stop the engine after the final flight of the day, be sure to stop by cutting the
fuel to remove fuel from the carburetor. And remove the fuel from the tank and reserve it with special care.
*When start the engine first after stop it by fuel cut, performing air purging is recommended. (Refer to the attached docu-
(2) Charge the battery for the ignition system and RC device fully. (Since the ignition system generates high tension, be careful
of electrical shock.)
(3) Lubrication for piston, connecting rod, bearing or cam gear is a blow-by lubrication in which the oil in the fuel goes into the
crankcase from the clearance between the cylinder and piston. Therefore the engine life is affected by the property of the
fuel oil. Please use reliable oil.
(4) Since over closing the main needle causes overheating, adjust a little more rich than peak. Over closing leads to knocking or
overheat and has an adverse effect on the connecting rod and cam gear. Where the airplane achieves peak completely at
the attitude of ascent should be a proper peak of the engine during flight.
(5) When connecting the exhaust pipe to the cylinder or attaching the prop nut, apply thin coat of silicon rubber (not exces-
sively) or adhesive on the thread section before tightening. This prevents leakage or loosening.
In case such like follows, reset the needle to the
Standard value (SDV).
・ After break-in
・ When adjustment can t be done correctly.
・ When by failure, turning the needle too much.
To set SDV, first fully close the needle.
(DO NOT close too tightly. The needles can be torn
After that open the needle to SDV as follows.
Throttle valve should be fully closed during setting
to SDV.
Main needle
 SDV for Main needle :
   2 turns open from full close
 SDV for Slow needle :
to rich
to lean
   4.5 turns open from full close
Standard value for the needles


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